Double dog detent for two-motion switches



Nov. 3, 1953 R. L. HUFFMAN DOUBLE DOG DETENT FOR TWO-MOTION SWITCHES 2Sheets-Sheet 1 Filed May 3,1949

INVENTOR. I ROBERT L. Hl JFFMAN M ATTORNEY Nov. 3, 1953 HUFFMAN2,657,590

DOUBLE DOGDETENT FOR TWO-MOTION SWITCHES Filed May 5, 1949 2Sheets-Sheet 2 INVENTOR. ROBERT L. HUFFMAN ATTORNEY Patented Nov. 3,1953 DOUBLE DOG DETENT FOR TWO-MOTION SWITCHES Robert L. Huffman,Chicago, Ill., assignor to Automatic Electric Laboratories, Inc.,Chicago, 111., a corporation of Delaware Application May 3, 1949, SerialNo. 91,096

1 Claim.

This invention relates in general to selective switching mechanism andmore particularly to two-motion selective switching mechanism and stillmore particularly to two motion selective switching mechanism for use inautomatic telephone systems.

More specifically, the invention relates to the provision of a new andimproved means for enabling the Switch-shaft in a switch of the Strowgertype to reach a predetermined position and be held in such a positionuntil released. Basically such a switch is shown in a patent to Keithand Erickson, No. 815,321.

One of the objects of the invention is to provide a new and improveddouble dog to assure accurate operation in a switch of the above character enabling the speed of the switch to be greatly increased.

Another object is to correct a condition known as stuttering whichdeveloped in the conventionally double-dogged switch when the releasetime of the actuating magnets is stepped up.

Still another object of the invention is to pro vide a double dog whichhas detents with differ ent moments of inertia so that the inertia ofone may be overcome without affecting the other.

A still further object of the invention is to provide a flexible rotarydetent in a double dog which can quickly spring into adjacent ratchetteeth without the delay of the conventional type which occurs while thedouble dog restoring spring is overcoming the inertia of the double dogsmass.

And still another object of this invention, while providing the otherfeatures mentioned above, is to provide a flexible rotary detent for adouble dog which will not readily become out of adjustment therebythrowing off other detailed adjustments.

These and other objects and features will be pointed out and explainedfully hereinafter in the specification, reference being had to theaccompanying drawings, Figures 1 to 5, inclusive, in which:

Fig. 1 is a left perspective view of a switching mechanism of theStrowger type with bank contacts and bank wipers left off.

Fig. 2 is a right perspective view of Figure 1 above.

Fig. 3 is a plan view of the members immediately co-operating in therotation of the switch shaft.

Fig. 4 is an end view of the double dog with its mounting pin.

Fig. 5 is a front View of the double dog also with its mounting pin.

The conventional double dog has been used in switches of the Strowgertype for a numper of years but has limited the speed at which such aswitch could operate for reasons which will immediately hereinafter bediscussed.

It has been known for some time, altho not visible to the naked eye,that the conventional double dog bounced two or three or more times eachtime it moved into engagement with a ratchet tooth on the switch shaft.A maximum rate of operation was generally conceded to be limited to aspeed whereby the actuating pawl initiating rotary motion to the switchshaft would be allowed to remain operated at its full stroke holding theshaft in its predetermined position sufficiently long before releasingfor the double dog to settle down and engage the adjacent ratchet toothto secure the switch shaft in the attained predetermined position. Thisholding time at the full stroke during rotary motion obviously slowsoperation of the switch by a length of time equal to the amount of thetime lost in one holding operation multiplied by the number of rotarysteps necessary to reach the ultimate predetermined position. No methodto remove this speed limitation was forthcoming over a period of greaterthan forty years. As soon as the operating speed of the switch wasincreased beyond the critical speed described hereinbefore by decreasingthe release time of the rotary actuating means, the rotary pawl wouldcomplete its stroke and begin its return before the double dog rotarydetent had stopped bouncing. The shaft would rotate back to thepreceding step having been deprived of the locking function of therotary detent which must, if at all, occur while the rotary actuatingpawl is at its full stroke. This cycle would then be repeated over andover creating what was dubbed a stuttering effect. With no correctivemeans forthcoming the industry accepted this limited speed of operationas the maximum attainable.

Experiments were made by applicant toward lightening the mass of thedouble dog so that it could respond more quickly by having its inertiaovercome more readily by the double dog restoring spring. However, thisdid not prove practical since the lighter metals would not hold shapeunder the pounding. The inventor then conceived the idea of substitutinga light, but strong hard steel spring member for the rotary detent. Sucha member, being light in mass could have its inertia over-come morereadily and if tensioned in addition, could overcome its own inertia dueto its stored up potential energy.

Experiments along this line of reasoning brought out ramifications inthe use of such a spring member. Springs bent into a right angle detentas well as springs bent at obtuse angles were tested. However, underactual operating conditions determined by life tests, springs with asharp bend therein of any angle rapidly lost their tension. Since thevariation in tension of the rotary detent would cause other members ofthe switch to become out of adjustment, use of a bent spring memberwould be impractical, for its employment would require either frequentreplacement or equally frequent complete readjustment of the switch,either of which is commercially unfeasible. Finally, a straight tensionspring and bracket member to properly position the spring in relation tothe rotary teeth was devised. The practicality of a, straight springrotary detent was proven beyond a doubt when it was life tested,operating successfully in over a million operations at an increasedswitch operating speed without recurrence of the stuttering conditionnor with appreciable variation in adjustment.

Referring again to the drawings, the new and improved double dog willnow be described in detail.

The double dog 1, shown in Figures 4 and 5 has as the major portion ofits mass a continuous member of metal stamped out of cold rolled steeland variously bent to form a vertical detent 2, to engage the horizontalcircular or vertical ratchet teeth H, a back stop member 3, an elongatedear 6 having a stud l, and two parallel horizontally bent ears 8 havingaxially aligned holes bored therein for mounting purposes. Fixedlyattached. to this continuous member is a tri-plane bracket member 4,side 4a being the side affixed. This aiiixation may be any standardmeans, preferably a spot weld. Side 4?] of the bracket member is in avertical plane which intersects a vertical plane including the axis ofthe cores of the rotary magnets at an angle of 45, in addition to whichthe bracket has two tapped holes side by side. Adjustably attached toside 4b of the bracket member is a light straight steel spring member 5of slight mass which at one end is mounted by means of two threadedbolts 9, thru the two holes near one end of spring member 5 into thetapped holes in side 4b of the bracket member. The spring is thentensioned so that it rests snugly against backstop 3 and positioned sothat the other end is parallel to the crests of rotary ratchet teeth 12while its length is such that when the vertical detent 2 is engaging avertical ratchet tooth H, the spring member 5 may upon rotation of shaftl engage and hold the radial surface of a rotary ratchet tooth. Therotary detent is therefore comprised of three members, backstop 3integral with the vertical detent 2; bracket member 4 and rotary detentspring 5. By the manner in which the various pieces are assembled the00mm pleted double dog comprises a vertical detent and a rotary detentrigidly attached together.

The double dog as detailed above is mounted to frame it by a pin M thruthe axially aligned holes in ears 3, pin M having a shoulder l and heldin place by clamp 16.

When the switch is at rest or normal, the detents of the double dog areheld out of engagement with their associated ratchet teeth by a releaselink spring I'i engaging stud 1 by means of a slot cut into the releaselink for that purpose.

Upon the first vertical motion imparted to shaft II] by energization ofvertical magnets l8 thru the medium of a vertical armature I9 and pawl20, a hook 2| on the vertical armature l9 lifts release link spring lloff of stud I. At this time double dog restoring spring 22 attached atone end to frame l3 and tensioned against vertical detent 2 of doubledog I forces vertical detent 2 into engagement with a vertical tooth I.

The vertical detent 2 will successively be forced out of the verticaltooth upon the next energization of the vertical magnets It but urgedinto the next tooth by the double dog restoring spring, this cyclerepeated until a predetermined vertical level is reached. The verticaldetent 2 by a combination of the inertia due to the mass of the doubledog and the force exerted by the double dog restoring spring thereonwill then continue to engage and hold the vertical tooth at the levelreached during subsequent rotary motion.

Rotary motion is imparted to the shaft 10 upon energization of rotarymagnets 23 thru the medium of rotary armature 24 and pawl 25 engagingrotary teeth !2 and rotating shaft Ill one radial step.

As the first rotary motion occurs stationary dog 26 which has beenriding in slot 21 slides under an adjacent circular tooth ll.

Simultaneousl as rotary motion is imparted in the manner describedabove, rotary detent spring member is forced away from its back stop 3as the flank of the first rotary tooth slides along the interior surfaceof spring 5 toward the free end thereof. At a point just as the rotarypawl reaches its full stroke, the end of rotary detent spring member 5slides over the crest of the tooth and under its own tension is driveninto the adjacent valley between the teeth where it engages the radialsurface of the tooth and holds it securely before the rotary pawl itsreturn stroke even where release time of the rotary magnet has beenappreciably decreased. Because of the light mass of the rotary detentspring and the positioning of its back stop member bounce is for allintents and purposes eliminated, and the light spring detent moves intoengagement faster. This cycle is repeated until a predetermined numberof rotary steps is reached. Each time the rotary detent spring willengage the next tooth just as the pawl reaches its full stroke, insuringaccurate operation at greatly increased speed. Further, because of thelarge difference in mass between the heavy rolled steel portion of thedouble dog l as compared to the light mass of the rotary detent springmember 5, and because of the greatly increased speeds at which therotary stepping is accomplished, the greater moment of inertia of thedouble dog is not overcome before the rotary detent spring secures atooth, whereby the vertical detent remains stationary and engaged with avertical tooth all during the rotary stepping; and further, because thevertical detents inertia is not overcome, no additional force need beexerted by the double dog restoring spring as it would be if thevertical detent were being pressed outward against it during rotarystepping. It is apparent then that the rotary detent spring member issecuring the rotary teeth under its own tension and independent of thedouble dog restoring spring; and likewise vertical detent 2 of thedouble dog is not perceptibly moved outward from a vertical tooth Hduring rotary motion.

Release is accomplished when the release magnet 28 is energized causingrelease armature 29 thru pin 30 to strike ear 6 of the double dog,forcing ear 6 inward and rotating detents 2 and 5 of the double dog onpin 1 out of engagement with teeth H and I2.

The shaft, now resting on stationary dog 26 rotates clockwise undercompulsion of helical spring 31 until stationary dog 26 falls into slot21 whereupon gravity carries shaft l0 downward until it comes to rest atits normal position.

Having described the invention and its operation in detail, what I claimand desire to be protected by issuance of Letters Patent is:

The combination with a switch shaft having vertical selecting andrelease movements and rotary selecting and release movements and havinga first series of teeth extending around the shaft and a second seriesof teeth extending lengthwise thereof, of a vertical detent for engagingsaid first teeth to hold said shaft in its vertical selecting positions,a rotary detent comprising a straight flexible spring secured rigidly tosaid vertical detent at one end of said spring and engaging said secondteeth at the other end thereof to hold said shaft in its rotaryselecting positions, a backstop for said spring detent integral withsaid vertical detent and positioned between said ends of said springdetent, said spring being tensioned against said teeth at said one endand against said backstop intermediate said ends,

said spring detent being movably flexed by said second teeth duringrotary selecting movement of said shaft, said vertical detent beingsubstantially independent of any flexing movement of the spring detent,and shaft release means for moving said vertical detent away fromengagement with said first teeth, said backstop moving with saidvertical detent to thereby remove said rotary detent from engagementwith said rotary teeth whereby said rotary detent is movable with saidvertical detent as a unit by means of the backstop when the verticaldetent is removed from engagement with said first teeth to therebyrelease said shaft.

ROBERT L. HUFFMAN.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 815,321 Keith et a1 Mar. 13, 1906 1,275,016 Goodrum Aug. 6,1918 1,290,507 Carroll Jan. 7, 1919 1,675,311 Sengebusch June 26, 19281,772,798 Carlson Aug. 12, 1930 1,818,690 Carlson Aug. 11, 19312,410,432 Drake Nov. 5, 1946 FOREIGN PATENTS Number Country Date 205,062Great Britain May 8, 1924

